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x86/cpufeatures: Fix dependencies for GFNI, VAES, and VPCLMULQDQ

PATCH Applied Eric Biggers 3 participants 3 messages Apr 17, 2024 – Apr 18, 2024

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Eric Biggers

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#0 lore raw

PATCH 1/1 x86/cpufeatures: Fix dependencies for GFNI, VAES, and VPCLMULQDQ

From: Eric Biggers <[email protected]>

Fix cpuid_deps[] to list the correct dependencies for GFNI, VAES, and VPCLMULQDQ. These features don't depend on AVX512, and there exist CPUs that support these features but not AVX512. GFNI actually doesn't even depend on AVX.

This prevents GFNI from being unnecessarily disabled if AVX is disabled to mitigate the GDS vulnerability.

This also prevents all three features from being unnecessarily disabled if AVX512VL (or its dependency AVX512F) were to be disabled, but it looks like there isn't any case where this happens anyway.

Fixes c128dbfa0f87 ("x86/cpufeatures: Enable new SSE/AVX/AVX512 CPU features")
Signed-off-by Eric Biggers <[email protected]>
---
 arch/x86/kernel/cpu/cpuid-deps.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
arch/x86/kernel/cpu/cpuid-deps.c +3 -3
index b7174209d855..946813d816bf 100644
@@ -42,11 +42,14 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_PCLMULQDQ,		X86_FEATURE_XMM2      },
 	{ X86_FEATURE_SSSE3,			X86_FEATURE_XMM2,     },
 	{ X86_FEATURE_F16C,			X86_FEATURE_XMM2,     },
 	{ X86_FEATURE_AES,			X86_FEATURE_XMM2      },
 	{ X86_FEATURE_SHA_NI,			X86_FEATURE_XMM2      },
+	{ X86_FEATURE_GFNI,			X86_FEATURE_XMM2      },
 	{ X86_FEATURE_FMA,			X86_FEATURE_AVX       },
+	{ X86_FEATURE_VAES,			X86_FEATURE_AVX       },
+	{ X86_FEATURE_VPCLMULQDQ,		X86_FEATURE_AVX       },
 	{ X86_FEATURE_AVX2,			X86_FEATURE_AVX,      },
 	{ X86_FEATURE_AVX512F,			X86_FEATURE_AVX,      },
 	{ X86_FEATURE_AVX512IFMA,		X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512PF,			X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512ER,			X86_FEATURE_AVX512F   },

@@ -54,13 +57,10 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_AVX512DQ,			X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512BW,			X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512VL,			X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512VBMI,		X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_VBMI2,		X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_GFNI,			X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_VAES,			X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_VPCLMULQDQ,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_VNNI,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_BITALG,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_4VNNIW,		X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_4FMAPS,		X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_VPOPCNTDQ,		X86_FEATURE_AVX512F   },

base-commit: 20cb38a7af88dc40095da7c2c9094da3873fea23

Signature · 1 line
2.44.0
Acked-by on v1 1/1
#1 lore raw
Quoted 7 lines · Eric Biggers

Fix cpuid_deps[] to list the correct dependencies for GFNI, VAES, and VPCLMULQDQ. These features don't depend on AVX512, and there exist CPUs that support these features but not AVX512. GFNI actually doesn't even depend on AVX.

This prevents GFNI from being unnecessarily disabled if AVX is disabled to mitigate the GDS vulnerability.

Looks like the original commit was quite confused. Thanks for finding this.

Acked-by Dave Hansen <[email protected]>
merge bot Applied
#2 lore raw
In reply to Eric Biggers
The following commit has been merged into the x86/urgent branch of tip:

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     9543f6e26634537997b6e909c20911b7bf4876de
Gitweb:        https://git.kernel.org/tip/9543f6e26634537997b6e909c20911b7bf4876de
Author:        Eric Biggers <[email protected]>
AuthorDate:    Tue, 16 Apr 2024 23:04:34 -07:00
Committer:     Borislav Petkov (AMD) <[email protected]>
CommitterDate: Thu, 18 Apr 2024 17:27:52 +02:00

x86/cpufeatures: Fix dependencies for GFNI, VAES, and VPCLMULQDQ

Fix cpuid_deps[] to list the correct dependencies for GFNI, VAES, and VPCLMULQDQ. These features don't depend on AVX512, and there exist CPUs that support these features but not AVX512. GFNI actually doesn't even depend on AVX.

This prevents GFNI from being unnecessarily disabled if AVX is disabled to mitigate the GDS vulnerability.

This also prevents all three features from being unnecessarily disabled if AVX512VL (or its dependency AVX512F) were to be disabled, but it looks like there isn't any case where this happens anyway.

Fixes c128dbfa0f87 ("x86/cpufeatures: Enable new SSE/AVX/AVX512 CPU features")
Signed-off-by Eric Biggers <[email protected]>
Signed-off-by Borislav Petkov (AMD) <[email protected]>
Acked-by Dave Hansen <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
---
 arch/x86/kernel/cpu/cpuid-deps.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
arch/x86/kernel/cpu/cpuid-deps.c +3 -3
index b717420..946813d 100644
@@ -44,7 +44,10 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_F16C,			X86_FEATURE_XMM2,     },
 	{ X86_FEATURE_AES,			X86_FEATURE_XMM2      },
 	{ X86_FEATURE_SHA_NI,			X86_FEATURE_XMM2      },
+	{ X86_FEATURE_GFNI,			X86_FEATURE_XMM2      },
 	{ X86_FEATURE_FMA,			X86_FEATURE_AVX       },
+	{ X86_FEATURE_VAES,			X86_FEATURE_AVX       },
+	{ X86_FEATURE_VPCLMULQDQ,		X86_FEATURE_AVX       },
 	{ X86_FEATURE_AVX2,			X86_FEATURE_AVX,      },
 	{ X86_FEATURE_AVX512F,			X86_FEATURE_AVX,      },
 	{ X86_FEATURE_AVX512IFMA,		X86_FEATURE_AVX512F   },

@@ -56,9 +59,6 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_AVX512VL,			X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512VBMI,		X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_VBMI2,		X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_GFNI,			X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_VAES,			X86_FEATURE_AVX512VL  },
-	{ X86_FEATURE_VPCLMULQDQ,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_VNNI,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_BITALG,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_4VNNIW,		X86_FEATURE_AVX512F   },